Gas springs are commonly used in various implementations in forming equipment to provide a movable component of a forming die with a yielding force, which is maintained throughout normal travel of the movable component. For example, in a binder ring implementation, a gas spring provides a yielding force against a binder ring of a forming die to hold a metal workpiece while another part of the forming die forms, cuts, stretches, or bends the workpiece. In a lifter implementation, the gas spring provides a yielding force to lift a workpiece off a surface of the forming die. In a cam tool implementation, the gas spring applies a yielding force to return a cam-activated tool to its home position.
Conventional gas springs, such as those disclosed in U.S. Pat. Nos. 5,275,387 and 5,303,906, typically have a piston rod disposed within a generally hollow cylinder including a closed rear end with a fill valve disposed therein, and a sealing assembly closing a forward open end of the cylinder and including a reinforcing or retaining ring and seals between the rod and the cylinder. Thus, a sealed gas chamber is defined between a rear end of the piston rod and the inside of the cylinder. The gas chamber receives a pressurized gas for yieldably biasing the piston rod to an extended position and for yieldably resisting movement of the piston rod from its extended position to a displaced or retracted position within the cylinder.
For example, upon closure of forming dies toward one another, a force is exerted on the piston rod, which force immediately yields a resultant reactive force of the gas spring. As the piston rod is displaced into the cylinder, the gas becomes further compressed. This gas compression by the piston causes the gas volume to decrease and, in accordance with Boyle's law, increases the gas pressure and thereby increases the resultant reactive force imposed on the die. And, the greater the piston displacement, the greater the reactive force. The sealing arrangements between the end cap and the cylinder, and between the piston rod and the cylinder prevents the release of the pressurized gas, thereby assuring the rise in gas pressure within the chamber.
The gas springs are capable of handling compression loads that are substantially parallel to the piston rod, but are not capable of resisting significant torque or side loading. Therefore, guide posts are often attached to the forming die and on either side of the gas spring to handle torque and side loading. Unfortunately, however, integration of guide posts directly into a forming die alongside a gas spring usually requires precious additional space on the forming die, costly customized design of the forming die and guide post assembly, and a fixed stroke length of the gas spring.